During the operation of combustion engines the quality of the combustion events depends on various conditions. One condition is how well the fuel is mixed with air in the combustion chamber. A poor air fuel mix may yield unwanted soot, and/or hydrocarbon emissions. This may be, in particular, during cold starts. One contributing factor to poor mixing is fuel impingement onto the top surface of surface of the piston as it moves within the combustion chamber. Long spray penetration, may result in the spray hitting the top surface of the piston, which may tend to keep the fuel at a cooler, liquefied, state. Fuel injectors have been used to inject fuel at high velocity in an attempt to atomize the fuel. Still, impingement onto the surface of the piston may still occur.
U.S. Pat. No. 7,458,364 to Allen discloses a fuel injection system wherein an attempt is made to improve atomization. The '364 disclosure includes a so called mixing chamber into which a positive displacement pump injects a measured amount of fuel. An air, or exhaust gas, conduit provides a gaseous make-up volume to the mixing chamber as a partial vacuum is produced in the adjacent combustion chamber to pull exhaust gas and fuel into the combustion chamber in a combined stream in an attempt to entrain the fuel into the exhaust stream. The vacuum is created in the combustion chamber by delaying the opening of an inlet valve as the piston starts a downward stroke. The mixing chamber includes an atomizing nozzle at an outlet side thereof, to accelerate the flow.
This approach has a number of shortcomings. For one, the '364 system requires a very particular operation of the charge air inlet valve in order to create a vacuum in the combustion chamber to cause air or exhaust to flow through the mixing chamber to entrain the fuel. The '364 design is intended to be used with smaller single cylinder engines that do not include a fuel pump. The positive displacement pump is designed for metered injection, not for increased pressure. In addition, there appears to be a relatively short time during which the fuel is exposed to the passing air or exhaust flow. There also appears to be little time for any appreciable heat transfer between the fuel and exhaust. The stream of exhaust and stream of fuel appear to be merely blended. It appears the fuel only becomes atomized as it passes from the atomizing nozzle into the combustion chamber within the blend.
The inventors herein disclose an engine, a fuel injector, and a method of injecting fuel into a combustion chamber of the engine that reduces the likelihood of impingement of the injected fuel onto the top surface of the piston, and provides an improved air-fuel mixture.
Embodiments may provide a fuel injector that may include an injector body. An end of the injector body may be configured to be positioned into a combustion chamber. A fuel sac may be defined within the injector body, and a main fuel passage may fluidically couple the fuel sac to the combustion chamber. The main fuel passage may have a varying cross-sectional area to form a reduced pressure region. An additional passage may fluidically couple the reduced pressure region with one of the fuel sac and the combustion chamber.
In this way, the low pressure region may cause some fuel to pass through the additional passage from the fuel sac into the main fuel passage, and may disrupt the flow to cause better mixing and/or more effective spreading of the fuel upon leaving the injector. Also, or instead, in this way the low pressure region may cause some warmed gasses from the combustion chamber to pass through the additional passage from the combustion chamber into the main fuel passage, and warm the fuel injected from the injector. Also, or instead, in this way, the low pressure region may create an area of low pressure to a side of the exit stream of the fuel from the injector outlet. In this way, the stream of fuel exiting the nozzle outlet may be made wider, may spread.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.